High Concentration Ethanol Production from Mixed Softwood Sawdust Waste

Abstract

Steam explosion pretreatment with high steam pressures, i.e. 35–55 atm, was conducted for the effective conversion of mixed softwood sawdust waste into ethanol. The results show the steam explosion with high steam pressures can significantly enhance the glucose yield after enzymatic saccharification and ethanol yield after alcohol fermentation. The effects of steam pressure on physical and chemical characteristics of steam-exploded sawdust were also clarified. Avoiding the effect of inhibitory materials produced by steam explosion with high pressures on enzymatic saccharification and alcohol fermentation, water and methanol extractions were attempted. The residue after water and methanol extractions of steam-exploded sawdust at a steam pressure 45 atm for a steaming time of 5 min was the most effective for the enzymatic saccharification followed by alcohol fermentation, and obtained a highest glucose yield, i.e. 81%. Simultaneous saccharification and fermentation using a high concentration of the residue resulted in an increased ethanol concentration and provided an ethanol production, i.e. 46.0 and 66.7 g/L, and a volumetric productivity of ethanol, i.e. 0.64 and 0.92 g/L h, from 200 to 300 g/L residue, respectively.